1. Field of the Invention
The present invention relates generally to pharmaceutical compositions, methods, and devices, and more specifically, to compositions and methods which reduce the likelihood of an infection associated with a medical implant.
2. Description of the Related Art
Infections associated with medical implants represent a major healthcare problem. For example, 5% of patients admitted to an acute care facility develop a hospital acquired infection. Hospital acquired infections (nosocomial infections) are the 11th leading cause of death in the US and cost over $2 billion annually. Nosocomial infections directly cause 19,000 deaths per year in the US and contribute to over 58,000 others.
The four most common causes of nosocomial infections are: urinary tract infection (28%); surgical site infection (19%); respiratory tract infection (17%); and bloodstream infection (16% and rising). A significant percentage of these infections are related to bacterial colonization of implanted medical implants such as Foley catheters (urinary tract infections); surgical drains, meshes, sutures, artificial joints, vascular grafts (wound infections); endotracheal and tracheostomy tubes (respiratory tract infection); and vascular infusion catheters (bloodstream infections). Although any infectious agent can infect medical implant, Staphylococci (S. aureus, S. epidermidis, S. pyogenes), Enterococci (E. coli), Gram Negative Aerobic Bacilli, and Pseudomonas aeruginosa are common causes. Once a medical implant becomes colonized by bacteria, it must frequently be replaced resulting in increased morbidity for the patient and increased cost to the healthcare system. Often the infected device serves as a source for a disseminated infection which can lead to significant morbidity or even death.
In an attempt to combat this important clinical problem, devices have been coated with antimicrobial drugs. Representative examples include U.S. Pat. No. 5,520,664 (“Catheter Having a Long-Lasting Antimicrobial Surface Treatment”), U.S. Pat. No. 5,709,672 (“Silastic and Polymer-Based Catheters with Improved Antimicrobial/Antifungal Properties”), U.S. Pat. No. 6,361,526 (“Antimicrobial Tympanostomy Tubes”), U.S. Pat. No. 6,261,271 (“Anti-infective and antithrombogenic medical articles and method for their preparation”), U.S. Pat. No. 5,902,283 (“Antimicrobial impregnated catheters and other medical implants”) U.S. Pat. No. 5,624,704 (“Antimicrobial impregnated catheters and other medical implants and method for impregnating catheters and other medical implants with an antimicrobial agent”) and U.S. Pat. No. 5,709,672 (“Silastic and Polymer-Based Catheters with Improved Antimicrobial/Antifungal Properties”).
One difficulty with these devices, however, is that they can become colonized by bacteria resistant to the antibiotic coating. This can result in at least two distinct clinical problems. First, the device serves as a source of infection in the body with the resulting development of a local or disseminated infection. Secondly, if an infection develops, it cannot be treated with the antibiotic(s) used in the device coating. The development of antibiotic-resistant strains of microbes remains a significant healthcare problem, not just for the infected patient, but also for the healthcare institution in which it develops.
Thus, there is a need in the art for medical implants which have a reduced likelihood of an associated infection. The present invention discloses such devices (as well as compositions and methods for making such devices) which reduce the likelihood of infections in medical implants, and further, provides other, related advantages.